This invention relates to an insulating bobbin for a rotary electrical machine and more particularly to a bobbin construction that facilitates the error free winding of electrical coils around the insulated pole teeth of an armature.
As is well known the armature of a rotary electric machine can comprise either a rotor or stator. It generally has a yoke comprising a ring shaped portion from which a plurality of circumferentially spaced magnetic pole teeth extend in a radial direction. The magnet pole teeth made of magnetic material such as iron are covered with insulating bobbins around which a coil of wire is wound. These bobbins are generally comprised of mating halves that are inserted from opposite sides of the yoke to substantially cover the yoke teeth. The wound coils cooperate with permanent magnets disposed in facing relationship to the magnet pole tooth.
As shown in co-pending application Ser. No. 10/709,919, entitled “INSULATOR FOR ARMATURE”, filed Jun. 5, 2004, in the name of the inventor hereof and another and assigned to the assignee hereof there are disclosed insulating bobbins for an armature that facilitate assembly. This application represents an improvement thereon that avoids a potential problem in the winding of the coils that may best be understood by reference to FIGS. 1–6, hereof.
Referring first primarily to FIG. 1, this is an exploded perspective view of the prior art armature, discussed generally above. The armature is indicated generally at 21. As illustrated, the armature 21 is provided for a three-phase motor and as an example only is part of a stator 22 with a wiring base 23 attached to one axial end (top end side in this figure) of the stator 22, through which the wound coils are interconnected in a manner as described in the co-pending application. The wiring base 23 is provided with three-phase (U, V, W) output terminals 24.
As shown in FIG. 1, the stator 22 is made up of a stator yoke or core 25 made as a body of laminated thin ferromagnetic plates. The stator yoke 25 is formed into a ring shape so as to surround the periphery of a rotor (not shown) and has integral, plural magnetic pole teeth 27 projecting radially inward. Slots 28 are formed between adjacent pairs of the magnetic pole teeth 27.
Generally like configured insulating bobbin halves, each indicated generally by the reference numeral 29, are telescopically fitted over opposite sides of the core 25. Each bobbin half 29 is formed with insert portions or lugs 31 formed in the same number as the slots 28 integrally with the side of the ring-like bobbins 29 facing the yoke or core 25. These lugs 31 are inserted into the slots 28, so that both bobbins 29 are secured and held to the stator yoke 25.
These upper and lower bobbins 29 cover each magnetic pole tooth 27 on the stator yoke 25 and a coil wire is wound up and down through the slots 28 present on both sides of each magnetic pole tooth 27, to form a plurality of circumferentially spaced coils, as will be seen later by reference to FIG. 4.
As best seen in FIGS. 2 and 3, each bobbin half 29 is of a ring shape made as a single body from a resin material and comprises a ring shape base portion 32 which covers an axial outer surface of the stator yoke 25, a coil winding portion 33 which covers each magnetic pole tooth 27 (FIG. 1) projecting inward from the base 32, and an end flange 34 continued from the coil winding portion 33, which covers a tip end (inner end) of each magnetic pole tooth 27.
Each flange 34 has a thick wall portion 34a formed above from the top surface of the coil winding portion 33 and side lugs 34b on both side of the thick wall portion 34a. These portions 34a and 34b locate and confine one end of the coil windings.
A protruding wall 35 is provided on the radially outer surface of the insulator base portion 32 on a root side of the coil winding portion 33. The protruding wall 35 is provided as a stopper or locator for the other radial end of the wound coil. It also is designed to catch and retain a bridge line for interconnecting one coil and another other coil on which a common coil wire is wound as well as to receive a coil end (upper surface portion of the coil winding portion 33 of each magnetic pole tooth) of each coil. As shown as an example shows the projecting walls 35 having slits 35a through which a winding end of the coil passes.
Referring now to FIG. 4, this illustrates the stator 22 having the wound and interconnected coils, indicated at 35. An end 36 of each coil 35 is drawn back to the root side of each magnetic pole tooth from the tip end side (inner end side) through a slit 35a so that it turns to a start of the coil winding for another coil 35 or is drawn out to be connected with the wiring base 23.
In addition to describing the prior art, the foregoing description relates also to the several embodiments of this invention, except as hereinafter described by reference to the several embodiments of the invention. The problems with the prior art and solved with this invention can be best understood by reference to FIGS. 5 and 6 which illustrate detailed views of the magnetic pole tooth of the bobbin 29. The coil 35 is formed around the bobbin coil winding portion 33. The end of the coil winding 36 for the coil 35 is drawn back to the root side of the magnetic pole tooth from the tip end side or the backside of the flange 34. It is possible, therefore, that this action could cause the coil winding end 36 to slide off over the coil 35 to its middle part as shown with a dotted line in the figure. This would result in a protrusion at the middle part of the coil. This causes a coil winding nozzle (not shown) to touch the displaced end of the coil winding 36 (shown by a dotted line) when the nozzle is inserted into the slot 28 to wind a wire on an adjacent coil, and damage the wire coating.
Therefore it is a principal object of this invention to provide a bobbin for an armature of a rotary electric machine which prevents a coil wire end from sliding off from the tip end side of the magnetic pole tooth to the root side and become damaged upon the winding of the next coil.